A medicine including citric acid magnesium oxide and sodium picosulfate is used as a purgative for pretreatment at the time of surgery, colonoscopy or colon X-ray inspection, and is currently commercially available as the name of Picolight power. This medicine is white powder which is used by being dissolved in water when taken orally.
The medicine in the dosage form of powder should be taken by dissolving one package in a suitable amount of water. However, some patients may feel inconvenient when dissolving the medicine in water, and some patients who fail to recognize how to use properly may drink water after putting the powder into the mouth. In this case, exothermic reaction occurring when the powder is dissolved in water may burn the patient's mouth.
Thus, the medicine in the form of powder may be dissolved in water in advance and stored in a refrigerator or another storage space before being taken. However, in this case, citric acid and magnesium oxide that are chief ingredients may react with each other to become magnesium citrate, and the remaining magnesium oxide after reaction may accelerate the precipitation of the magnesium citrate over time to sink to the bottom. Therefore, if the medicine is not diluted well with water when taken, a proper effect cannot be achieved because the precipitated amount cannot be taken. As the pH of the medicine is kept low, the amount of precipitation tends to be reduced. However, in this case, there arises a problem such that sodium picosulfate becomes unstable.
Therefore, in order to solve the problems described above, there is a demand for a physically and chemically stable pharmaceutical liquid composition.